This application claims the priority of German application 197 39 131.1-16, filed Sep. 6, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a headrest for a vehicle seat which is pivotally mounted and includes a cushion and an air filled variable volume hollow body.
In the case of a known headrest of this type (German Patent Document DE 39 00 495 A1), the hollow body constructed as an air bag is used as an actuator for the cushion support whose swivelling position determines the inclination adjustment of the head cushion. The air bag is connected to a compressed-air source by means of a manually operable ventilating and deventilating valve. In addition, the air bag is connected to a compressed-air storage device which, in the event of a crash, abruptly inflates the air bag, whereby the air bag emerges on the bottom side from the head cushion and, in the manner of a hose, extends into the seat user's neck lordosis area in order to achieve an additional support there. The activating of the compressed-air storage device in the event of a crash takes place by means of an acceleration sensor.
In the case of another also known headrest (German Patent Document DE 22 20 267 A1), the elastic hollow body arranged between the cushioning and the supporting bow is filled with a medium, such as a gas or a liquid, and is connected by way of a so-called resistance part with an empty hollow part which also consists of an elastic material, such as rubber, artificial resin, or the like. The elastic material of the hollow part has a larger contraction force than the material of the hollow body. The resistance part may be constructed as a return valve, a control valve, a flap valve, a return flap valve, a backflow valve, or the like which can be opened manually in the opposite direction. In the event of a crash, the shock exercised by he seat user's head onto the head cushion is converted into pressure onto the medium in the hollow body, whereby the medium can flow off by way of the resistance part into the hollow part. As a result, the kinetic force of the head impact onto the head cushion is partially absorbed and its effect onto the sitting person is reduced. For the return flow of the medium, which flows over into the hollow part, back into the hollow body, the resistance part must be opened manually, in which case, because of the higher contraction force of the hollow part material, the medium flows back into the hollow body relieved from the head pressure.
It is an object of the invention, to ensure in the case of a headrest, which has a head cushion of the initially mentioned type which can be adjusted in its inclination, in a constructively simple manner, that, in the event of a crash, the head cushion adjustment is reliably maintained and the adjusted inclination therefore is not reset.
In the case of a headrest of the type referred to above, this object is achieved according to the invention by an arrangement, wherein the swivel bearing of the cushion support is constructed such that, in the case of a normal head contact force, the cushion support maintains its adjusted swivelling position, and wherein the hollow body is provided with a throttle opening which counters a shock-type air discharge with an extremely high flow resistance and counters an air discharge and an air entry of a low flow rate with only a low flow resistance.
The headrest according to the invention has the advantage of a very simple construction. By means of the hollow body with the throttle opening, the inclination of the head cushion can easily be adjusted in the normal case. The construction of the swivel bearing provides that the head cushion adjustment is not changed when the head user places his head against it, but the head cushion maintains the selected adjustment. The hollow body follows the slow swivel movement of the cushion support during the head cushion adjustment, in which case, according to the swivelling direction, because of the low flow resistance of the throttle opening, the air can escape out of the hollow body or represent an afterflow into the hollow body. In the event of a crash, when the head suddenly strikes against the head cushion, the flow resistance of the throttle opening will be so high that air cannot escape to a significant extent. The cushion support with the cushioning is therefore reliably locked and is not displaced toward the rear. The hollow body, which is preferably made of PUR-material, can be produced at reasonable cost, in which case it is either self-inflating in its given shape or is inflated by the cushion support during its swivelling. The throttle opening is easily illustrated and can be implemented by means of a small hole in the hollow body wall.